I have an ascending aurora aneurysm diagnosed 2 years ago at 4.0 cm. Before that the heart check up ultrasound tests I was doing every couple of years were at about 3.5. It is now around 4.2. I was also shocked to see this because I have always exercised (running for 30 years and years road cycling 10 years) I have gotten a bit different guidance from heart experts. All agree that blood pressure must be kept normal, no heavy lifting (over 100 lb) and no smoking (I never smoked). The specialists at a major heart hospital also told me to keep heart rate below 120 bpm but my local cardiologist does not agree and said I could go back to road cycling as a I was doing before. I doing a lot of walking now and keeping tabs on the numbers but not sure I will get back on the bike outdoors since we have a lot of hills.